Envelope Tracker Calibration for Power Amplifier Gain Compression
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Solution Overview
Problem
Maintaining consistent gain compression in power amplifiers when varying the supply voltage in relation to the RF signal envelope is challenging due to part-to-part component variations, leading to misalignment and complications in calibration, especially with variations in DC offset voltage, insertion loss, and gain in the envelope and signal paths.
Innovation Solution
A method for calibrating an envelope tracking system involves generating a supply voltage using an envelope tracker with an envelope shaping table, operating at a first voltage level with no gain compression, decreasing voltage levels, measuring output power, and determining a second voltage level for desired gain compression, then calibrating the tracker based on these measurements to maintain consistent gain compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking is used to improve power amplifier efficiency by varying supply voltage with RF signal envelope, then power efficiency is improved, but gain compression consistency deteriorates due to part-to-part component variations
Solution Approach 1:
The patent applies preliminary action by pre-calibrating the envelope tracker to compensate for component variations before actual operation. The calibration process determines correction factors that are stored and applied during normal envelope tracking operation, ensuring gain compression consistency is maintained without requiring real-time adjustments.
Solution Approach 2:
The patent implements feedback by measuring the actual gain compression of the power amplifier and using this measurement to adjust the envelope tracker calibration. The system continuously monitors performance and applies corrections to maintain the desired gain compression characteristics despite component variations.
2Stability of the object's composition
If calibration is performed to account for component variations, then gain compression consistency is improved, but calibration complexity and time increase
Solution Approach 1:
The calibration is performed as a preliminary one-time operation during manufacturing or initial setup, rather than requiring continuous calibration during operation. This approach accepts the time investment upfront to eliminate the need for frequent recalibration, thereby reducing overall time loss.
Solution Approach 2:
The system performs self-calibration by automatically measuring its own gain compression characteristics and adjusting its internal parameters without requiring external intervention. This self-service capability reduces calibration time and complexity compared to manual calibration procedures.
3Measurement precision
If envelope shaping table is generated at desired gain compression, then gain compression accuracy is improved, but misalignment due to component variations increases
Solution Approach 1:
The patent applies parameter changes by adjusting the envelope shaping table parameters based on measured component variations. Instead of using fixed theoretical values, the system modifies the shaping table parameters to compensate for actual component characteristics, thereby maintaining both accuracy and reliability.
Solution Approach 2:
The system uses feedback from actual gain compression measurements to update and refine the envelope shaping table. This iterative process ensures that the shaping table remains accurate despite component variations, as it is continuously adjusted based on real performance data.
Data Source
AI summary
Methods of calibrating a power amplifier system to compensate for envelope amplitude misalignment are provided. In certain configurations, a method of calibrating a power amplifier system includes amplifying a radio frequency signal from a transceiver using a power amplifier and generating a supply voltage of the power amplifier using an envelope tracker, including generating a scaled envelope signal based on a power control level signal and an envelope signal, and shaping the scaled envelope signal using a shaping table generated at a target gain compression. The method further includes changing a scaling of the scaled envelope signal using a calibration module, monitoring an output of the power amplifier to determine an amount of scaling of the scaled envelope signal at which a detected gain compression of the power amplifier corresponds to the target gain compression of the shaping table, and calibrating the power amplifier system based on the determination.